1. Field of the Invention
This invention relates to a color liquid-crystal panel and a manufacturing process therefor. In particular, it relates to a color liquid-crystal panel comprising a switching element such as a thin-film transistor (TFT), a color filter and a black matrix on a single substrate.
2. Description of the Prior Art
A color liquid-crystal panel is conventionally constituted by first substrate 1 having a switching element such as a TFT comprising a gate electrode 2, a gate insulating film 3, a semiconductor layer 4 and source-drain electrodes 5 and 6, interconnection layers to the individual electrodes (not shown), all of which are covered by an interlayer film 7, pixel electrodes 11 to individual pixels, which are covered by a passivation film 12, an oriented film 18a, and a terminal 13 for interconnection with an external circuit; and a second substrate 16 comprising a black matrix 8, color filter layers 10R, 10G and 10B for individual colors R, G and B, respectively, a transparent common electrode 17 such as an ITO, and an oriented film 18b, where these substrates are put together via an intervening spacer 14 for ensuring a given gap between them and a sealer 15 surrounding their peripheries in a manner that their device-forming surfaces face, as shown in FIG. 11. Then, the sealer is burned, a gap between both substrates is determined and then a liquid-crystal material 19 is poured into the panel.
Liquid crystal may be injected by, e.g., a two-hole method where two holes are formed in selected places in the panel and liquid crystal is injected from one hole while the panel is vacuumed from the other hole to facilitate feeding the liquid crystal, or a vacuum-injection method where an empty cell having an inlet and liquid crystal are vacuumed to 1xc3x9710xe2x88x922 to 1xc3x9710xe2x88x924 Torr to deposit the liquid crystal around the inlet and then the vacuum of the system is gradually broken to the atmospheric pressure so that a pressure difference between the inside and the outside of the liquid-crystal cell induces transfer of the liquid crystal into the inside of the cell. The latter method has been predominantly employed.
After injecting liquid crystal, the inlet is sealed and then polarizing plates 20a and 20b are attached to the outer faces of the substrates to provide a liquid-crystal panel.
To improve definition of a liquid-crystal panel, it is necessary to provide a higher pixel density. A conventional liquid-crystal panel where a color filter and a black matrix are disposed on a substrate facing to an active-matrix substrate must be manufactured with a given margin for an alignment error which may occur during an assembling process. It has been, therefore, difficult to ensure the maximum area of the pixel opening (opening ratio).
Thus, there has been proposed a method where a color filter and a black matrix are formed on an active-matrix substrate comprising a switching element such as a TFT (CF-on-TFT; hereinafter, referred to as xe2x80x9cCOTxe2x80x9d).
Due to forming a color filter and a black matrix on a COT substrate, it is not necessary to consider an assembling margin, leading to a more simplified manufacturing process and increase in a pixel opening ratio.
However, forming a color filter or black matrix directly on a TFT or an interconnection may cause malfunctioning of the switching element because elements or ions in the color filter or black matrix enter into the main component of the switching element. Thus, JP-A 10-39292 has proposed that a protective film, i.e., a passivation film, is formed between a switching element and a color filter.
An object of this invention is to disclose a specific structure for such a COT type of liquid-crystal panel. The above application (JP-A 10-39292 has not described an edge structure for a liquid-crystal panel.
This invention provides a color liquid-crystal panel comprising the first substrate having pixel electrodes on which are formed a thin-film transistor as a switching element for each pixel, which is covered by a passivation film, and a color filter layer and a black matrix on the passivation film, which are covered by an overcoat layer, and where the first substrate and the second substrate having a transparent common electrode facing the first substrate are put together via a sealer, forming an inner space which is filled with a liquid-crystal material, wherein a frame-shaped black matrix covers the periphery of the first substrate.
According to this invention, a liquid-crystal panel suitable for a COT configuration can be provided.